A post shared by John Stamos (@johnstamos) on Jan 21, 2018 at 9:27pm PST

He posted a black-and-white photograph on Instagram of the newborn lying on his chest and wrote: “From now on, the best part of me will always be my wife and my son. Welcome Billy Stamos (named after my father) #NotJustanUncleAnymore#Overjoyed.”